The present invention relates to a method for controlling a drive coil of a contactor.
An electronic drive control for a magnetic drive is known from European Patent Application EP 0 789 378 A1.
If the control voltage of a contactor is drawn from one of the three phases, synchronization effects can ensue between the closing or opening angle of the main contacts in the load circuit and the AC control voltage.
This is due to the fact that a certain voltage build-up of the supply voltage for the electronics has to take place.
If the control voltage is switched on at voltage zero, then the supply voltage does not build up immediately but only at a later point in time. Around this point in time, an unwanted synchronization takes place as a result of which one of the three switching contacts of the contactor is always subject to higher wear. This means, that one contact has a switch-on point at which the voltage level is approximately identical, independently of the instant of the control signal. Since the service life of the contactor depends on the service life of the most eroded contact, the synchronization results in shortened service life of the overall device.
An object of the present invention is to provide a method for electronic drive control of a drive coil of a contactor with which the service life of the contactor is increased.
The present invention provides a method for controlling a drive coil of a contactor having main contacts for a load current. The method includes providing an electronic drive control apparatus including a microcontroller. A randomly selected constantly varying time delay is applied in the microcontroller after a time at which a supply voltage has built up at the electronic drive control apparatus and before a time at which the supply voltage is measured.
Via the present invention, an irregular erosion of the switching contacts is prevented and, consequently, the service life of the contactor is increased.
With reference to the drawings, embodiments of the present invention will be described and illustrated in greater detail.